For millions of Americans the site of a policeman and -- A sense of calm faith that order is being kept -- the good guys are watching but for many others. Thousands stopped on the streets of New York because they look or act a certain way. In -- with the blue white breed fear frustration and anger -- a force that some say is bent more on intimidation and serving and protecting. -- here's my co anchor Bill -- -- -- yeah -- it's the kind of scene that could play out on any given day in any city in America. All men in blue stopping young men of color who. As tensions in Iraq and in this case a robbery suspects competently enough really. -- -- -- -- Yeah. And. The others released. And the cops managed to keep it by the book. Didn't understand your upset -- -- convenience but this scene is just pretend. It is an NYPD training drill to reinforce a proper way to do what is known as -- 250. That controversial tactic designed to stop crime before it happens. Controversial. Because critics say to fifties rarely happen with this much courtesy and this much probable cause. They say the NYPD stops and frisks way too many innocent men of color for no good reason. Who's holding these talented puck is going up down one go to -- with very little -- and -- shed light on the devastated an hour and Laguna restful we'll be. You know -- doesn't. -- -- -- -- -- -- An excellent -- -- -- my hand them ahead solidly this old time. Frustrated by how often he was being stopped in his Harlem neighborhood a sixteen year old son of a cop named Alvin says he hit record on his iPod one night in 2000 left. As to undercover officers approached. We will about a little. He's excited and -- spotlight -- -- listening. We don't want the plot which -- -- It is one of the few known recordings of something that happens nearly 2000 times a day in New York but whether this is the exception -- rule. It's a debate dividing America's biggest city. I don't think it was a unique stop -- or any of that other young people that I've talked to personally. -- activists filmmakers Aaron Schneider and Ross Tuttle heard the record and they spent eight months convincing Alvin to go public. For their short documentary the hunted. And the hated that we -- was this you know the worst could encounter you've you've had with MI -- so actually no it's not he said I've had worse. Like you like a Prisoner of War and -- could -- -- why you. -- What happens to officers in -- -- like that. There is a civilian complaint process and indeed there is a civilian complaint review board Ray Kelly as the man in charge of the NYPD. We have. A system to address that now I'm not talking specific about this. Case because I don't know about it but we're human beings that we make mistakes and we may have people who. Inappropriately. Stop individuals but by and large I don't believe that is that's the case it is event specific. Since taking over 2002 Kelly has presided over the most dramatic reduction in crime in modern American history. Where she was director load proving it down 25% this year like his predecessor Bill Bratton Kelley believes in proactive policing. And done properly the 250 is a Supreme Court approved method of stopping crime before it happens. But here is the controversial. Of these thousands of daily stop and frisks only 6% lead to an arrest and little over 1%. Actually turn up weapons. Critics say this is proof it doesn't work mayor Michael Bloomberg. Disagrees. That's the reason we needed to deter people from carrying guns. We are the first prevent jurors in a fiery speech this week Bloomberg chastised NYPD critics they seem to believe the department should be run according to the stand as a political correctness not public safety cops say is first for ventures only works with -- strong backing of City Hall. Especially in the face of this statistic. Even though blacks and Hispanics are a minority here a majority of people stopped around 84%. Are young men of color. How many times have you stopped -- -- -- -- upon -- And your old. Something it is neighborhood of Flatbush Brooklyn Cassini Walters has witnessed gang shootouts and watch young men his age lea street phantom of -- all of them Austin. But after a number of rough to fifties an -- back here. And Eminem banging my head into that he says he's more afraid of the law. Than thugs and a few blocks away. He shows me the memorial of the 250 -- -- that fills him with even more dread. That it's still there. When -- money gray adjusted his waist band on this -- in March. Two undercover officer stepped up for a stop and frisk and ended up shooting him seven times. They claim -- -- this loaded 38 revolver later recovered at the scene. But Kassim doesn't believe them. Four days of angry demonstrations. Proves he's not alone when things like this happen live -- -- top companies and are never gonna get the benefit of doubt that we have a relationship with a cocky. You know until Ray Kelly can give us answers at New York City councilman -- money William wants as a mentor of casinos and a leading critic of the NY PDA's methods like police reports which show that the reason given for most stops is either a high crime neighborhood. Or a suspect engaged in furtive movement. And I have tourette's syndrome. So I don't make -- -- it's so -- not be that can be stopped every time -- come out of my -- what we wanted to break up crime in the meantime -- organized crime. I don't believe -- stopped every town in person that they -- I don't believe they did that they would have gotten away with so I think we deserve the -- respected -- in the -- I've been around a long time -- this department our relations now about an -- -- then. One of the reasons is our police officers are now minority majority this is the most ever city in the world. We are now more reflective that diversity than ever before. But more minority cops doesn't mean all of them are supporters of stop. -- I was stopped by police officers because of mavericks because what -- looked like they stereotyped they racially profiled I knew that I don't want to do that. Pedro Serrano is one of two cops now denouncing his own department's policies and he says he. He made -- hidden recording of his own -- People who -- -- right OK he is convinced that there is a perverse quota system in place which drives officers to stop minority kids for no good reason. You don't come with those numbers they retaliate. By giving you bad evaluations. That's -- so wouldn't it to me. After writing just to 250s over an entire year Serrano called for a meeting with his deputy inspector to appeal a bad a valuation. He also says he wore a wire. And recorded this. And he didn't mind if you had more problems -- annual. Laden there hockey and more people robbing them I'm me. Will handle. -- -- he. All right there arm as when -- lost it. You want me to stop everybody the good people and the bad people so you can get -- numbers the nine year veteran as a witness for the center for constitutional rights and advocacy group now suing the NYPD not for money. But to change -- stop and frisk policies -- Serrano and his attorney say this is proof. Of racial profiling the NYPD insist the inspector was talking about specific suspects in -- specific string of crimes. And that Serrano was -- to collect damning evidence for lawsuit for contacts. Inspector also said this. -- People of the community her -- We'll still we'll. This -- yes and stuff to people. You know he all he shouldn't baby gone wrong that all persons not doing your job. This is a business we have almost a five billion dollar -- a year so we run it like a business and it's fair. Ask the employees here to do their -- -- How does a number of 250s. Among the week a year affect an officer's career if an officer continually. It doesn't do what the commander. Watson to do and I don't think it's going to. Positively affect its Korea for sure but I don't think it negatively affected if you don't the numbers here back. That's just how they see it but Pedro Serrano has no doubt he has negatively affected his career by breaking the thin blue line. -- got -- guys out there who want to hurt me because someone that they uniform. And you've got the hierarchy was certainly because I. -- the truth and let the commissioner Kelly insists that race is not a factor in this camp it's just that most of his offices are set where most crimes are reported. And that up to 75%. Of violent crime victims described their attacker. As a black males the percentage of people who saw. It's 53%. After getting ever so really. African Americans are being under stop in relation to. Percentage of people being described as being the perpetrators of violent crime the -- reality is. That crime happens in communities. Of -- they are being disproportionately. Victim. God gave me he had not pretty. Just curious what you would say to the kids good kid. -- grew up in these rough neighborhoods and resents the fact that he gets stopped 56 dozen times as your life and forms his opinion of authority around those exchanges what would you say that -- -- trying to save his life. We're trying to save the lives of other young people. Who applaud disproportionately victimized on the streets of this city and other cities throughout America.

This transcript has been automatically generated and may not be 100% accurate.